Thin film electrode for high-quality GaN optical devices

Abstract

A thin film electrode for ohmic contact of a p-type GaN semiconductor includes first and second electrode layers sequentially stacked on a p-type GaN layer. The first electrode layer may include an Ni-based alloy, a Cu-based alloy, a Co-based alloy, or a solid solution capable of forming a p-type thermo-electronic oxide or may include a Ni-oxide doped with at least one selected from Al, Ga, and In. The second electrode layer may include at least one selected from the group consisting of Au, Pd, Pt, Ru, Re, Sc, Mg, Zn, V, Hf, Ta, Rh, Ir, W, Ti, Ag, Cr, Mo, Nb, Ca, Na, Sb, Li, In, Sn, Al, Ni, Cu, and Co. Furthermore, a method of fabricating the thin film electrode is provided.

Description

BACKGROUND OF THE INVENTION[0001]This application claims the priority of Korean Patent Application No. 2003-47273, filed on Jul. 11, 2003 with the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.1. FIELD OF THE INVENTION[0002]The present invention relates to a thin film electrode and a method of manufacturing the same capable of forming high-quality ohmic contact, which is one key technique in fabricating light emitting diodes (LEDs) and laser diodes (LDs) that emit short waves of blue, green and ultraviolet rays using a GaN semiconductor.2. DESCRIPTION OF THE RELATED ART[0003]When embodying optical devices such as LEDs and LDs using a GaN semiconductor, it is important to form a high-quality ohmic contact between a semiconductor and an electrode.[0004]In the case of a conventional p-type GaN semiconductor, a Ni-based thin metal film structure, i.e., a thin metal film of Ni / Au, was widely used. Currently, various ohmic...

AI Technical Summary

Benefits of technology

[0011]The present invention provides a thin film electrode capable of forming high-quality ohmic contact having a large work function value and high transmissivity in a short wavelength region of light and made of p-type thermo-electronic oxide while the effective carrier density around a surface of a GaN semiconductor is increased by destroying Mg—H combinations by making use of an excellent affinity for hydrogen of an alloy or solid solution that forms the p-type thermo-electronic oxide thin film.

[0032]According to the present invention, after an alloy or a solid solution that forms a p-type thermo-electronic oxide thin film is deposited on a p-type GaN layer, annealing is carried out, thereby adjusting the energy band gap between the p-type GaN and the p-type thermo-electronic oxide and increasing the effective carrier density in a surface thereof. As a result, the Schottkey barrier height and width between the p-type GaN and the p-type thermo-electronic oxide are reduced. Therefore, there is provided a high-quality ohmic contact system having high transmissivity in a short wavelength region of light while providing excellent current-voltage characteristics and low specific contact resistance.

[0033]According to the present invention, using the excellent electricity conductive and thermostable properties, the p-type thermo-electronic oxides can replace typical metal electrodes. Also, Ni, Co, and Cu, which are thermodynamically favorable for forming a GaN-related compound, are used as major base metals of the p-type thermo-electronic oxides to allow for the production of a large quantity of Ga vacancies in a surface of the p-type GaN.

Problems solved by technology

However, two problems heretofore hinder a p-type GaN ohmic contact from ensuring high quality contact.

Thus, a Mg—H complex having an electrically insulating characteristic is formed, which results in a low effective carrier density and a high surface resistance value.

Therefore, it is difficult to form a high-quality ohmic contact.

Actually, the low hole injection makes the fabrication of high-quality optical devices difficult.

A second problem is that there is no a high-quality ohmic contact system having high transmissivity in a short wavelength region of light.

An ohmic contact using such an extremely thin metal layer can obtain high transmissivity but is one reason for degrading efficiency of an optical device because of difficult current injection and propagation.

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